Some gyroscopes (gyros) require erection systems which slave an axis of the gyro ("erect" the gyro) to a desired attitude. For a vertical gyroscope, for example, the gyro rotor spin axis is slaved to the vertical.
Various types of erection systems have been used for this purpose. Some erection systems are electromagnetic and use a gravity switch and an electromagnetic torquer. Other erection systems are electromagnetic and use a pendulous pickoff element for controlling a torquing element, while yet other systems use an electrolytic switch wherein the variable resistance of an electrolytic fluid controls the torquing element. Still other erection systems are mechanical such as the "ball disc" erection system or the "pin ball" erection system and feature variations to disconnect or disable the erection system to avoid false slaving during maneuvers of a vehicle, such as an aircraft, using the gyro for navigational purposes.
Some erection systems employ the flow of air produced by the spinning gyro rotor to generate reaction forces. These forces are gravity controlled by vane like devices to direct appropriate air jets which erect the gyro. However, these systems are not capable of being disconnected under excessive turn or acceleration conditions of the vehicle, as are likely to occur.